Internal combustion engine



A.` HoFsTETTER NTERNAL COMBUSTIONY ENGINE Filed April 2e, 1939 `June 3,1941.

Patented June `3, 1941 UNITED STATES PATENT OFFICE' 2,243,846 y INTERNALCOMBUSTIQN ENGINE Alfons Hofstetter, Gaggenau, Baden, Germany, assignor`to Daimler-Benz Aktiengesellschaft, Stuttgart-Unterturkheim. vGermanyApplication April 26, 1939, Serial No.v270,105

claims.

This invention relates to Internal combustion engines and particularlyto such engines of the precombustion chamber type.

It is an object thereof to provide an improvedI engine of this typeincluding a burner through which the precombustin chamber contents are'expelled into the main combustion space such as the cylinder space,which burner is formed with a series of successively restrictedcross-sections which has a simple configuration which may be turned sothat the cost of manufacture will be Very low as compared with previousdevices which frequently required many parts some of.v

which involved the provision of intricate passages which increasedthe'cost of manufacture.

Another object is to provide such a burner in which the tread portion ofone or more of said steps is undercut to further enhance the atomizationand intermixing of the charge.

Another object is to so construct the precombustion chamber burner thatit may be made of ordinary steel.

A further object is to so construct the burner that its wall thicknessincreases toward the main combustion space so that it 'is thickest whereit is subjected to the high temperatures of the main combustion space.

Another object is to provide a burner so formed that due to thedistribution of the material of its walls it will serve as a heatstoring body for preheating the air as it is driven from the maincombustion space to the precombustion chamber.

A further object is to provide a burner so constructed that'when theengine' is cold and is turning slowly a part of the fuel is sprayedthrough an opening co-axial with the fuel jet directly into the maincombustion space where it is ignited for starting the engine whereaswhen the engine is heated or speeded up `ignition and precombustion willoccur in the precombustion chamber.

Another object is to provide such a construction in which the outer endof the burner is pro- Such stepsscause eddies whichv Germany May 2, 1938vided with a plurality of openings through which the precombustionchamber contents are ejected into the `main combustion space, one vofwhich openings is preferably cor-axial with the fuel injection nozzle.

Another object is to provide a precombustion chamber constructioncomprising a sleeve inserted into a member of the engine such as thecylinder head, one vend thereof serving to receive the burner, the otherend serving to receive the fuel injection nozzle and the intermediateportion .l thereof serving to form the precombustion chamber.

Other objects will appear from the following description. ofanillustrative embodiment of the invention taken together with theattached drawing wherein:

Fig. 1 shows an engine illustrating a precombustion chamber constructionmade in accordance with the invention; Y

Fig. 2 shows the precombustion chamber insert and the burner, as shownin Fig. l, on a somewhat enlarged scale;

Fig. 3 shows the burner alone;

Fig. 4 shows a plan View of the burner; and

Fig.y 5 shows a modified form of burner in which a number of exitpassages are provided.

Referring to Fig. i, a, indicates a cylinder of any desiredconstruction, b the cylinder head, c

tween the intake and exhaust valves g. In the,

form of construction illustrated, the precombustion chamber e is formedwithin an inserted sleeve i within the upper part of which isv housedthe fuel spray nozzle f, being preferably fastened therein by screwthreads formed within said sleeve' and upon .said fuel nozzle, whereasthe lower portion `of said sleeve vi serves to receive and carryias byscrew threads h" the burner h. As will be notedfrom' the drawing,the-cross sectional arealof the burner is formed with a series ofsuccessively restricted cross-sections, defining a series of steps h',the tread portions of which face upwardly whereas their riser portionsare arranged generally vertically. Inl the form shown, the treadportions of said steps are It is of course to be un-y the tread surfaceswould be planar. As shown, the lower or outer end of the burner h isformed with an opening k for communication with the main combustionspace.

As will be apparent, the successive reduction of the cross-section ofthe burner passage results in a gradual thickening of the wall thicknessof the burner so that a greater thickness is available near the maincombustion space where the greatest temperatures prevail. Thus, theburner'walls themselves may serve as aheat storing body to preheat theair passing therethrough to the precombustion chamber. By suitablystepping down the outside diameter as indicated in the drawing thewall'thickness may be adjusted to any amount desired to provide therequired heat storing capacity.

In operation, the precombustion chamber contents as they pass from theprecombustion chamber to the main combustion space strike the treadsurfaces of said step-like conformations and are deflected therefrom insuch a way as to form eddies and in other ways to provide a thoroughmixing of said contents and further atomization of the fuel particles,whereafter, said contents are ejected through the central bore k intothe main combustionspace d.A In this manner, thorough mixing andatomization can be effected without providing a number of .in-

tricate passages which set up undue resistance.l

It will also be noted that the various parts may be turned and thereforemay be produced much cheaperl than those devices involving complex andtortuous passages.

As shown in Fig. 5, a number of' exit passages may be provided such asthe axial passage I' and annula'i'ly and angularly arranged passages l.

In certain cases it will .besulcient to form the burner without theconically shaped stepped portions. Furthermore, the precombustionchamber may be arranged at any desired` angle. with respect to the 4axisof the cylinder and the exit openings k, l, and l may be rearranged andcombined 'in any desired way. Furthermore, the central exit opening l inthe form shown in Fig. 5, .or for that matter, valso the opening Ic inFigs. 2 and 3 may be formed conically, preferably in such a manner thatits cross-sectional area increases toward the main combustion space sothat its smallest cross-.section is toward the precombustion chamber.This central exit opening makes possible easy starting of the engine,even in the cold condition,

since during starting. if the temperature reached within theprecombustion chamber is insufficient to igm'lte .the fuel, a partthereof may be sprayed directly through the central opening into themain combustion space where due to the higher temperatures prevailingthere, it will be ignited, thus assuring starting of the engine. As soonas normal operating speed is reached, precombustion will occur in. theprecombustion chamber since the counter current of air from the maincombustion space toward the precombustion chamber may be made sucientlypowerful to prevent the penetration of the fuel jet into the maincombustion space so that the usual normal operation of the precombustionchamber engine takes place. y l* It will be noted that the constructionsshown and described will serve admirably to accomplish the objectsstated above. It is to be understood, however, that the constructiondisclosed above is intended merely as illustrative of the invention andnot as limiting as various modiflcations therein may be made withoutdepart-A ing from the invention as defined by a proper interpretation ofthe claims4 which follow.

passage formed with a series of successively re stricted cross-sectionsdefining a series of steps the diameters of which decrease toward saidcombustion space, whereby the tread portions of said steps face towardthe fuel injection means and at least one port connecting said passagewith said main combustion space.

l2. In an internal combustion engine of the fuel injection type having amain combustion space, a precombustion chamber, fuel injection meansarranged for injectingfuel into said precombustion chamber, and a burnerarranged between said precombustion chamber and said main combustionspace, said burner havingv a passage formed with a series ofsuccessively restricted cross-sections defining a series of undercutsteps the diameters of which decrease toward said combustion space, andthe tread portions of which steps slope outwardly and downwardly andface toward the fuel injection means and at least one port connectingsaid passage with said main combustion space.

3. In an internal combustion engine of the fuel injection type having amain combustion space, a precombustion chamber, fuel injection meansarranged for injecting fuel into` said precombustion chamber, and aburner arranged between said precombustion chamber and ,said maincombustion space, said burner having a passage formed with a series ofsuccessively restricted cross-sections defining a series of steps thediameters of which decrease Ytoward said combustion space, whereby thetread portions of said steps face toward the fuel injection means and aplurality of openings connecting said burner passage with the maincombustion space,

one of which openings extends in the axis of thev jet injected by saidfuel injection means.

4. In an internal combustion engine of the fuel injection type having amain combustion space, a precombustion chamber, fuel injection meansarranged for injecting fuel into said precombustion chamber, and aburner arranged be- L tween said precombustionv chamber and said maincombustion space, said burner having a passage formed with a series ofsuccessively restricted cross-sections defining a series of steps arearranged substantially concentric with the` axis of the fuel jetdelivered byvsaid fuel injectiqn means.

6. In an internal combustion engine the combination according to claim 1in which the said port is arranged substantially within the axis ofjecting fuel into said precombustion chamber, a

conduit extending from said precombustion chamber to said maincombustion space so constructed that fuel may be injected from said fuelinjection means directly into the main combustion space, said conduitbeing reduced in internal cross-sectional area toward said maincombustion space by a plurality of inwardly extending step-likecongurations of its inner sur-` face.

9. In an internal combustion engine the combination according to claim 8in which said inwardly extending step-like configurations are arrangedsubstantially concentric with the axis of the fuel jet delivered by saidfuel injection means.

10. `In an internal combustion engine the combination according to claim8 ln which sai conduit is provided with a port leading into th maincombustion space, said port being arranged substantially within the axisof the fuel jet deligered by said fuel injection means.

11. In an internal combustion engine the combination according to claim8 in which said in- Y wardly extending step-like 'configurations arearranged substantially concentric with a line extending from the fuelinjection means to the said port.

12. In an internal combustion`engine of the fuel injection type having amain combustion space, the combination of a precombuston chamber, fuelinjection means arranged for in,

jecting fuel into said precombustion chamber. the said precombustionchamber consisting of a section of relatively large diameter adjacentthe fuel injection means and a Vportion which comprises a conduitextending to said main combustion space, the said conduit being reducedindiameter from the diameterof the portion adjacent the fuel injectionmeans toward said main combustion space by a plurality of inwardlyextending step-like congurations ofiits inner surface. i

13. In an internal combustion engine the com.

bination according to claim 12 in which inwardly extending step-likeconfigurations are arranged substantially concentric with the axis ofthe `fuel jet delivered by said fuel injection means.

14. In an internal combustion engine the com' bination according toclaim 12 in which the successive diameters of said inwardly step-likeconfigurations decrease substantially the same amount and the smallestdiameter comprises a y port leading into the main combustion space.`

15. In an internal combustion engine the combination according to claim12 in which said inwardly. extending step-like congurations are formedin a separate inserted member.

ALFONS HOFS'IETTER..

